Dr. Leonard Perry, Extension Professor
University of Vermont
Yes, there are orchids you can grow outside in the garden. These are called hardy or terrestrial (meaning in the ground) orchids. Growing this group of plants can be easier than you think, provided you choose the right species and pay attention to a few cultural needs.
When people think of orchids, they invariably think of the ones among the 20,000 tropical species and even more hybrids that must be grown indoors in northern climates. Most don't realize there are over 200 species of terrestrial native orchids that grow in North America. Since some of these may be endangered in certain states, it is essential to purchase plants from ethical sources-- nurseries that have either saved species from habitat destruction, or more often propagated and grown them in their nurseries. One authority for such sources is the New England Wildflower Society (www.newfs.org/).
To dispel two common misconceptions, hardy orchids can be grown in gardens outside their natural habitats, and they can be transplanted. Tips for which species to choose for what kind of conditions, and their culture, can be found in the book by William Mathis, The Gardener's Guide to Growing Hardy Perennial Orchids (TheWild Orchid Company, Doylestown, Pennsylvania, www.wildorchidcompany.com).
One principle for growing hardy orchids is that many not only thrive in temperate, even frigid climates, but some may need below-freezing temperatures to meet cold requirements for bloom (much like tulips and many other perennials).
Another key point in success with hardy orchids is that they don't need much fertilizer. In fact, they don't tolerate heavy fertility. Usually some compost incorporated at planting, and applied around them in future years, is all that is needed. If you have nutrient-poor soil, you may fertilize plants lightly with one-quarter strength or rate that you would use normally for flowers.
The main principle for success with hardy orchids is good soil drainage. This may involve building up a raised bed with a good soil, or excavating and replacing some garden soil with a better mix. This doesn't imply extensive digging, it could be as simple as making a large hole with good soil. Sand and perlite are two ingredients often used both to increase soil drainage, and to hold the soil moisture that most species need.
The soil moisture relates to the three main habitats that include many of the hardy species. The upland species are those that do not tolerate constantly moist soil. If your soil doesn't drain well normally, these may not be the best choice. A hole filled with water should drain in under four hours. Upland orchids usually grow best in full to part shade, but this will vary with hardiness zone and species. Some hardier species include the Lady Slippers and hardy Chinese orchids.
Transition species are those that can tolerate more constant moisture, but thrive under drier conditions similar to the upland species. When flowering, if in a drought, they may need some watering. Otherwise these species thrive in often harsh conditions, and are good choices for many gardens. A good moisture-retentive soil mix, even if added to the planting hole, is often needed. Hardy transition orchids include the Egret flower, Fragrant Ladies Tresses, Marsh orchid, and Purple Fringed orchid.
Wetland species, as their name implies, require constantly moist or even wet soil. They prefer full sun. Unless you have a normally wet soil, you should line the raised bed or planting hole with plastic to retain moisture. Poke a few holes in the bottom to allow slow water drainage, as these do not like to sit in stagnant water. In nature their roots are in edges of streams or ponds where water is moving, even if slowly. One of the hardiest wetland species is the Rose Pogonia.
Three additional tips will help you have success with hardy orchids.
After blooming, remove old flowers. This keeps plant energy going
into the roots and not into seed production. When weeding, grasp
and hold the orchid plant while pulling weeds. This helps you from
pulling up the orchid with the weed. The orchid roots are generally
shallow, with the weed roots growing under them. Then for extra winter
protection you may wish to add a couple inches of weed-free straw or pine
needles on top. If using leaves, make sure they are ones that don't
pack down tightly.
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